1-Benzoyl-3-hydroxy-6(1H)-pyridazinones employed as plant growth regulators

ABSTRACT

A novel class of growth regulator compounds of the structural formula ##STR1## is disclosed, in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH 2  OH, --CHO, --R, --OR or halogen and R is C 1  to C 4  alkyl or alkenyl.

This is a division of application Ser. No. 124,991, filed Mar. 13, 1980, now U.S. Pat. No. 4,256,884.

DESCRIPTION OF THE INVENTION

The use of 1,2-dihydro-3,6-pyridazinedione, commonly called maleic hydrazide, as a plant growth regulator and inhibitor is widespread and has been responsible for significant improvements in the production of certain specific agricultural crops. Many derivatives of this active substance have also been known for some time, none of which has shown any substantial improvement or useful difference in growth regulating activity, in comparison with the parent compound. It has been known, for example that the benzoyl derivative, 1-benzoyl-3-hydroxy-6(1H)-pyridazinone, having the structural formula ##STR2## has growth inhibiting activity approximately equal to maleic hydrazide, as measured by inhibition of bud growth on soybeans. (Canadian J. Biochem. and Physiol. v. 40 p. 1159-1165, September 1962, also U.S. Pat. No. 2,614,917.) When applied to soybean plants which are in the process of setting pods, or on which pods are set, this compound causes the pods to shrink, turn brown and drop.

We have discovered a novel class of compounds that differs from the aforementioned compound only by the presence of a single substituent group, which possesses growth regulating activity of a distinctly different type, so that these compounds may be used, for example, to increase the setting and filling of pods on soybeans, as well as for other purposes, such as selective post-emergent control of wild oats.

Briefly, the novel growth regulators of the present invention are compounds having the structural formula ##STR3## in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH₂ OH, --CHO, --R, --OR or halogen and R is C₁ to C₄ alkyl or alkenyl.

SYNTHESIS OF THE NOVEL GROWTH REGULATORS

The growth regulator compounds are readily synthesized from commercially available intermediates or by reaction of maleic hydrazide with ortho-substituted benzoic acids which are easily made by conventional methods. An illustrative procedure appears below.

SYNTHESIS OF 1-(2-CARBOMETHOXYBENZOYL)-3-HYDROXY-6(1H)-pyridazinone

Into a 100 ml round-bottomed flask fitted with a stirrer and reflux condenser there was charged 10.8 g (0.06 mole) of 2-carbomethoxybenzoic acid and 50 ml of chloroform. There was then added 7.8 g (0.066 mole) of SOCl₂, followed by refluxing for 2 hr. The chloroform was then removed by distillation, followed by addition of 50 ml. of dimethoxyethane, 4.7 g (0.06 mole) of pyridine and 6.7 g (0.06 mole) of maleic hydrazide. The mixture was allowed to stir over night. The resulting reaction mixture was filtered to remove solids. Then the product was precipitated from the filtrate by addition of water and was recovered as a solid by filtration. The solid material was washed with hexane-ether solvent mixture and was filtered and dried. The yield was 6.6 g, m.p. 144°-145° C. Infrared and nuclear magnetic resonance spectra were consistent with the structure of the compound as named above.

USE OF THE GROWTH REGULATORS

By application of an effective amount of the growth regulators, either pre- or post-emergently, various effects on young plants become apparent. These effects may be demonstrated by means of the following illustrative procedures.

PRE-EMERGENT APPLICATION

Disposable paper trays about 21/2 inches deep which were filled with soil were sprayed with aqueous spray mixtures at a rate of 10 lb. of active chemical per acre of sprayed area, then were seeded with 6 species of plant seeds and were covered with about 1/4 inch of soil. The spray mixtures were prepared by dissolving the proper amount of growth regulant compound in 15 ml of acetone, adding 4 ml of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 60 ml by addition of warm water. Twenty-one days after seeding and treatment the plantings were examined and plant injury was rated according to the following schedule.

    ______________________________________                                         DEGREE OF EFFECT                                                               ______________________________________                                         0 =      no effect                                                             1 =      slight effect, plants recovered                                       2 =      moderate effect, injury to 26 to 75 percent                           3 =      severe effect, injury to 76 to 99 percent                                      of foliage                                                            4 =      miximum effect (all plants died)                                      ______________________________________                                    

POST-EMERGENT APPLICATION

Several species of plants were grown in potting soil in disposable styrofoam trays and tomatoes were grown in four-inch pots in the greenhouse. Aqueous spray formulations were prepared and the growing plants were sprayed at a spray volume of 60 gallons per acre and an application rate of 5 lb. per acre. Spray mixtures were prepared in the manner described above. For comparative purposes, plants were also sprayed at 60 gal./acre with a spray mixture containing no growth regulator. Plant injury was again rated according to the schedule disclosed above.

Observations of growth regulator effects in both pre- and post-emergent tests were observed and recorded as follows:

    ______________________________________                                         Effect               Abbreviation in Tables                                    ______________________________________                                         Formative effect on new growth                                                                      F                                                         Epinasty             E                                                         Growth reduction     G                                                         Necrosis             N                                                         Non-emergence        K                                                         Chlorosis            C                                                         ______________________________________                                    

In the table below there are tabulated various observations of pre- and post-emergent herbicidal and growth regulator effects of the compounds disclosed above.

                                      TABLE I                                      __________________________________________________________________________     GROWTH REGULANT EFFECTS OF COMPOUNDS OF THE FORMULA                             ##STR4##                                                                      __________________________________________________________________________     Com-                  Pre-emergent Effects                                     pound           M.P.  Digitaria                                                                            Celosia                                                                             Bromus                                                                              Setaria                                                                             Raphanus                                                                            Beta                           No.    Y        °C.                                                                           sanguinalis                                                                          plumosa                                                                             inermis                                                                             italica                                                                             sativus                                                                             vulgaris Comments              __________________________________________________________________________     3712 COOCH.sub.3                                                                               144-145                                                                              G3F2  G2   K3G3 G3   G2   G2F1                           4082 COOC.sub.2 H.sub.5                                                                        117-119                                                                              0     G1   0    G1   G1   G1                             4139 COOH       >200 dec.                                                                            F1G1  F2G2 F3G3 F3G3 F1G1 N2G2     Promotes                                                                       axillary              4237 CH.sub.3   162-164                                                                              0     F1   0    F1   0    0        growth                4238 Cl         >210 dec.                                                                            G1    G2   G1   G3   G3   G2                             4240 COOCH.sub.2 CH.sub.2 CH.sub.3                                                             102-105                                                                              G1    G2   G2   G3   G2   G1                             4282 OCH.sub.3  160-170                                                                              G2    G2   G2   G3   G2   G1                             __________________________________________________________________________     Com-                  Post-emergent Effects                                    pound           M.P.  Setaria                                                                              Medicago                                                                            Avena                                                                               Raphanus                                                                            Beta Lycopersicum                   No.    Y        °C.                                                                           italica                                                                              sativa                                                                              sativa                                                                              sativus                                                                             vulgaris                                                                            esculentum                                                                              Comments              __________________________________________________________________________     3712 COOCH.sub.3                                                                               144-145                                                                              G2    G2   G3F1 G2   F2G1 N1                             4082 COOC.sub.2 H.sub.5                                                                        117-119                                                                              0     0    0    0    0    0                              4139 COOH       >200 dec.                                                                            G1    F1G1 G3F1 0    F1   F1       Promotes                                                                       axillary              4237 CH.sub.3   162-164                                                                              N1G1  N1   G3   N1   N1   F1       growth                4238 Cl         >210 dec.                                                                            G1    0    G1   0    F1   0                              4240 COOCH.sub.2 CH.sub.2 CH.sub.3                                                             102-105                                                                              G1    G1   --   G1   N1G1 F2G1                           4282 OCH.sub.3  160-170                                                                              G1    0    --   0    0    F1G1                           __________________________________________________________________________

The use of many of the growth regulator compounds may be demonstrated by treatment of soybeans (Soja max) to increase the number of seed pods and by treating tomato plants (Lycopersicum esculentum) to increase fruit set. In an illustrative experiment, Soja max (Evans variety) and Lycopersicum esculentum (Tiny Tim variety) were grown in 4-inch pots (one plant per pot) filled with greenhouse potting soil (2 parts good top soil, 11/2 parts builders' sand, 11/2 parts peat, fertilized with 5 lb. of 12-12-6 fertilizer and 5 lb. of finely ground limestone per cu. yd.). Aqueous spray formulations were prepared and the potted plants were sprayed at a spray volume of 40 gal. per acre and at application rates of 16, 4, 1 and 1/4 oz. per acre. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml. of actone, adding 2 ml. of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor El-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 80 ml by addition of a 0.156 wt. percent aqueous solution of liquid non-ionic dispersant (90 wt. percent active trimethylnonyl polyethylene glycol ether, Tergitol TMN-10). Two replicates were sprayed at all application rates. For comparative purposes, plants were also sprayed at 40 gal./acre with water. The number of seed pods and of fruit as percentage of arithmetic mean of the numbers on untreated plants were observed within approximately three weeks after spray treatment and the results are tabulated below. The severity of growth regulatory effect on the plants was estimated on a scale of 0 to 10 and is also recorded in the following table:

                  TABLE II                                                         ______________________________________                                         GROWTH REGULATING EFFECTS ON TWO SPECIES                                               Soja max         Lycopersicum esculentum                                             Pod Count.sup.1                                                                          Sev-            Sev-                                                 Percent   erity of                                                                              Fruit Count.sup.1                                                                       erity of                                             in Com-   Growth Percent in                                                                              Growth                                               parison to                                                                               Regu-  Comparison                                                                              Regu-                                  Comp'd Rate   Untreated lating to Untreated                                                                            lating                                 No.    oz/A   Plants    Effect.sup.2                                                                          Plants   Effect.sup.2                           ______________________________________                                         44082  16      23.sup.3 1.5    64       0                                             4       77.sup.4 1      86       0                                             1      100.sup.5 1      150      0                                      44139  16     150       0.5    107      0                                             4      100       0      129      0                                             1       91       0      107      0                                      43712  16      64.sup.3 1      0        1                                             4      96.sup.3  0      109      0                                             1      114       0      150      0                                      44237  16      41.sup.3 1      0        1                                             4      118.sup.3 0      27       0                                             1      118       0      136      0                                      44238  16      68.sup.3 0.5    0        1                                             4      145.sup.3 0      177      0                                             1      105       0      123      0                                      44239  16      23.sup.3 1.5    0        1                                             4       96.sup.3 0.5    0        0                                             1      132       0      14       0                                      44240  16      27.sup.3 1      0        0.5                                           4       82.sup.3 0      95       0                                             1       96       0      123      0                                      44282  16      55.sup.3 0.5    14       0.5                                           4      100.sup.3 0      95       0                                             1      141       0      136      0                                      ______________________________________                                          .sup.1 Checks = 100                                                            .sup.2 Greenhouse rating on scale of 0, no effect; 10, total kill.             .sup.3 Axillary growth; aborting pods.                                         .sup.4 Pods without beans.                                                     .sup.5 More buds.                                                        

The information presented in tabular form herein will enable a worker in the art to make a selection from among the growth regulator compounds of the invention and to make some judgment with regard to application rates, depending upon the effect which is desired. It may be seen, for example, that total kills of some species of vegetation may occur at application rates as high as 5 to 10 lb. per acre, whereas beneficial effects may be observed on living plants at application rates of 1 lb. per acre or less.

The growth regulator compounds are usually formulated as 0.1 to 95 weight percent active ingredient in combination with a surface active agent and one or more inert carriers or diluents, as in emulsifiable formulations, granules and dust formulations, in accordance with established practice in the art. An aqueous spray is usually prepared by mixing a wettable powder or emulsifiable concentrate formulation of a growth regulator with a relatively large amount of water to form a dispersion.

Wettable powders comprise intimate, finely divided mixtures of growth regulator compounds, inert solid carriers and surface active agents. The inert solid carrier is usually chosen from among the attapulgite clays, the kaolin clays, the montmorillonite clays, the diatomaceous earths, finely divided silica and purified silicates. Effective surfactants, which have wetting, penetrating and dispersing ability are usually present in a wettable powder formulation in proportions of from 0.5 to about 10 percent by weight. Among the surface active agents commonly used for this purpose are the sulfonated lignins, naphthalenesulfonates and condensed naphthalene-sulfonates, alkylbenzenesulfonates, alkyl sulfates and nonionic surfactants such as products of condensation of ethylene oxide with alkylphenols.

Emulsifiable concentrates of the growth regulator compounds comprise in each instance, a solution of growth regulator compound in a liquid carrier which is a mixture of water-immiscible solvent and surfactants, including emulsifiers. Useful solvents include aromatic hydrocarbon solvents such as the xylenes, alkylnaphthalenes, petroleum distillates, terpene solvents, ether-alcohols and organic ester solvents. Suitable emulsifiers, dispersing and wetting agents may be selected from the same classes of products which are employed in formulating wettable powders.

In general, the growth regulators are seldom applied without the presence of a carrier or surfactant. However, direct application to plant seeds prior to planting may be accomplished in some instances by mixing powdered solid growth regulator with seed to obtain a substantially uniform coating which is very thin and comprises only one or two percent by weight or less, based on the weight of the seed. In most instances, however, a nonphytotoxic solvent, such as methanol is employed as a carrier to facilitate the uniform distribution of growth regulator on the surface of the seed.

When a compound is to be applied to the soil, as for a pre-emergence application, granular formulations are sometimes more convenient than sprays. A typical granular formation comprises the growth regulator compound dispersed on an inert carrier such as coarsely ground clay, or clay which has been converted to granules by treatment of a rolling bed of the powdered material with a small amount of liquid in a granulating drum. In the usual process for preparing granular formulations, a solution of the active compound is sprayed on the granules while they are being agitated in a suitable mixing apparatus, after which the granules are dried with a current of air during continued agitation. 

We claim:
 1. The method of regulating plant growth comprising applying to plants an effective amount of a compound having the structural formula ##STR5## in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH₂ OH, --CHO, or --OR, and R is C₁ to C₄ alkyl or alkenyl.
 2. A plant growth-regulating composition comprising from 0.1 to 95 weight percent of a compound having the structural formula ##STR6## in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH₂ OH, --CHO, or --OR, and R is C₁ to C₄ alkyl or alkenyl, in combination with a surface active agent and an inert carrier.
 3. The method of increasing fruit set on agricultural crop plants comprising applying to the plants an effective amount of a compound having the structural formula ##STR7## in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH₂ OH, --CHO, or --OR, and R is C₁ to C₄ alkyl or alkenyl.
 4. The method of claim 3 in which the crop plants are of the species Soja max.
 5. The method of claim 3 in which the crop plants are of the species Lycopersicum esculentum.
 6. The method as specified in claim 1 in which Y is --COOCH₃.
 7. The method as specified in claim 1 in which Y is --COOC₂ H₅.
 8. The method as specified in claim 1 in which Y is --COOH or an agriculturally acceptable salt thereof.
 9. The method as specified in claim 1 in which Y is --COOCH₂ CH₂ CH₃.
 10. The method as specified in claim 1 in which Y is --OCH₃.
 11. The method as specified in claim 3 in which Y is COOCH₃.
 12. The method as specified in claim 3 in which Y is --COOC₂ H₅.
 13. The method as specified in claim 3 in which Y is --COOH or an agriculturally acceptable salt thereof.
 14. The method as specified in claim 3 in which Y is --COOCH₂ CH₂ CH₃.
 15. The method as specified in claim 3 in which Y is --OCH₃. 